Solid deformation imaging

ABSTRACT

Process and articles for forming line, halftone or continuoustone images which comprises: exposing to actinic radiation in image-receiving manner a solid, positive-acting or negativeacting light-sensitive organic layer having a thickness of at least 0.1 micron, said layer being capable of developing a Rd of 0.2 to 2.2; continuing the exposure to either clear the background of positive-acting light-sensitive layers or to establish a potential Rd of 0.2 to 2.2 with negative-acting light-sensitive organic layers; applying to said layer of organic material, free-flowing powder particles having a diameter, along at least one axis of at least about 0.3 micron but less than 25 times the thickness of said organic layer; while the layer is at a temperature below the melting points of the powder and of the organic layer, physically embedding said powder particles as a monolayer in a stratum at the surface of said light-sensitive layer to yield images having portions varying in density in proportion to the light exposure of each portion; and removing nonembedded particles from said organic layer to develop an image.

United States Patent Hayes et al.

[151 3,637,385 [451 Jan. 25, 1972 SOLID DEFORMATION IMAGING [72] Inventors: Lester P. Hayes, Decatur, 111.; Rexlord W. Jones; William B. Thompson, both of Columbus, Ohio A. E. Staley Manufacturing Company, Decatur, 111.

[22] Filed: Feb. 5, 1969 [21] App1.No.: 796,847

[73] Assignee:

[52] U.S. Cl ..96/48, 96/88, 96/115 [51] Int. Cl. ..G03c 5/24, G03c 1/68 [58] Field oiSearch ..96/48, 1,2, 115 P, 115,88;

Primary Examiner- Norman C. Torchin Assistant ExaminerRichard E. Fieht Attorney-William H. Magidson and Charles J. Meyerson ABSTRACT Process and articles for forming line, halftone or continuoustone images which comprises: exposing to actinic radiation in image-receiving manner a solid, positive-acting or negativeacting light-sensitive organic layer having a thickness of at least 0.1 micron, said layer being capable of developing a R,, of 0.2 to 2.2; continuing the exposure to either clear the background of positive-acting light-sensitive layers. or to establish a potential R,, of 0.2 to 2.2 with negative-acting lightsensitive organic layers; applying to said layer of organic material, free-flowing powder particles having a diameter, along at least one axis of at least about 0.3 micron but less than 25 times the thickness of said organic layer; while the layer is at a temperature below the melting points of the powder and of the organic layer, physically embedding said powder articles as a monolayer in a stratum at the surface of said light-sensitive layer to yield images having portions varying in density in proportion to the light exposure of each portion; and removing nonembedded particles from said organic layer to develop an image.

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DESCRIBE INDUSTRIOUS NATIV'ES UNIQUE description of a s'trange people PROMISING TESTIMONY READILY GIVEN Quuxzn decision sought in recent. market case SOLID DEFORMATION IMAGING DISCLOSURE OF THE INVENTION This invention relates to a method of forming solid, deformation images wherein the deformation image is developed by embedding particles of a predetermined size into a stratum at the surface of a powder-receptive, solid, light-sensitive organic layer. More particularly, this invention relates to a method of forming direct-reading, positive, continuous-tone, solid, deformation images without forming a negative intermediate, wherein the continuous tone deformation image is developed by mechanically embedding particles of a predetermined size directly into a stratum at the surface of a powderreceptive, solid, light-sensitive organic layer.

Although numerous photographic reproduction processes utilizing a wide variety of sensitizers have been developed, conventional continuous tone black and white or color reproductions are produced with silver halide emulsions. When compared to other light-sensitive systems, silver halide emulsions can be developed to provide continuous tone images by well-established practical techniques. However, silver halide emulsions generally are negative acting and are developed either by diffusion transfer or in suitable chemical baths to produce a negative, followed by printing a positive. Accordingly, there is a need for a simple commercial process for forming permanent continuous tone black and white or color reproductions directly on a light-sensitive element.

There are several photographic processes where a latent image is formed directly in or on a light-sensitive thermoplastic element and developed after converting the thermoplastic portion of the exposed light-sensitive thermoplastic element into a liquid or semisolid softened state necessary for development. The developed image is made permanent by hardening the liquid or semisolid thermoplastic material. These techniques are used in plastic deformation imaging where a latent image is formed by exposure to actinic radiation and developed by the application of a suitable force. For example, image development can result from the production of discontinuities on the surface of a thermoplastic light-sensitive element, such as frost patterns" or rippled images in xerography, or within the thermoplastic light-sensitive element, such as gas bubbles in vesicular prints. The discontinuities in the frost deformation images scatter light and become visible when subjected to transmitted light, preferably provided by an optical viewer or projector.

In very simplified form, prior art deformation imaging processes employ a light exposure step followed by temporary softening ofthe thermoplastic layer by heat or solvent, which permits a suitable force, such as electrostatic or gas pressure, to deform the thermoplastic light-sensitive element. The images or discontinuities are frozen into or on the thermoplastic layer by hardening said layer, usually by cooling the melted layer. U.S. Pat. No. 3,317,315 indicates that xerographic deformation processes have the advantage, when compared to conventional xerographic processes, that they do not require means for applying toner or means for fixing the toner to form a permanent image. However, light-scattering deformation imaging processes have the obvious drawback that they require a softening step, usually heating, and yield images that lack the black-white contrast demanded by the public for viewing with the naked eye. In some cases, frost patterns can be produced without a temporary softening step by suitable choice of thermoplastic material, but the images lack permanence.

U.S. Pat. No. 3,060,024 discloses forming a latent image by exposing a thermoplastic light-sensitive element comprising a thermoplastic polymer and a plasticizing addition polymerizable monomer to light until substantial polymerization takes place in the exposed areas. The latent image is developed by heating the light-sensitive element to soften or liquify the underexposed thermoplastic areas, dusting or sprinkling the element with a suitable powder, such as carbon black, cooling the light-sensitive element to freeze the particles into the unde rexposed areas and removing unattached powder from the nonimage areas. The patentees indicate that this process is suitable for the production of line images or half tone reproductions.

U.S. Pat. No. 2,090,450 discloses that acetals of nitrobenzaldehydes can be changed by exposure to light to render the exposed area either adhesive or nonadhesive. The exposed element is developed by dusting with a suitable powder, such as soot.

The general object of this invention is to provide a method and elements for forming deformation images wherein the deformation image is developed by embedding particles of a predetermined size into a stratum at the surface of a powderreceptive, solid, light-sensitive organic layer One important object of this invention is to provide a method of forming direct-reading, positive, continuous-tone deformation images without forming a negative intermediate, wherein the continuous-tone deformation image is developed by embedding particles of a predetermined size directly into a stratum at the surface of a powder-receptive, solid, light-sensitive organic layer. Another object of this invention is to provide a method of forming deformation images directly in or on a stratum at the surface of a powder-receptive, solid, light-sensitive organic layer where a softening step is not necessary to place the lightsensitive element in the proper state for development of the latent image. Other objects will become apparent below.

In the description that follows, the phrase powder-receptive, solid, light-sensitive organic layer is used to describe an organic layer which is capable of developing a predetermined contrast or reflection density (R upon exposure to actinic light and embedment of black powder particles of a predetermined size in a single stratum at the surface of said organic layer. While explained in greater detail below, the R of a light-sensitive layer is a photometric measurement of the difference in degree of blackness of undeveloped areas and black powder developed areas. The terms physically embedded or physical force are used to indicate that the powder particle is subjected to an external force other than, or in addition to, either electrostatic force or gravitational force resulting from dusting or sprinkling powder particles on a substrate. The terms mechanical embedded or mechanical force are used to indicate that the powder particle is subjected to a manual or machine force, such as a lateral to-andfro or circular rubbing or scrubbing action. The term "embedded is used to indicate that the powder particle displaces at least a portion of the light-sensitive layer and is held in the depression so created, i.e., at least a portion of each particle is below the surface of the light-sensitive layer.

In one aspect, this invention is a light-sensitive element capable of forming deformation images by embedment of a monolayer of powder particles of at least 0.3-micron diameter along at least one axis which comprises a solid, light-sensitive organic layer having a thickness of 0.1 to 40 microns, said layer being capable of developing a R, of 0.2 to 2.2 upon exposure to actinic light and of accepting and retaining powder particles physically embedded in single stratum at the surface of said layer, the concentration of the particles being proportional to the exposure, while the layer is in at most a slightly soft condition and is at a temperature below the melting point of the layer and powder.

In a second aspect, this invention is a process for forming deformation images which comprises: exposing to actinic radiation in image-receiving manner a solid, positive-acting, light-sensitive organic layer having a thickness of at least 0.1 micron, said layer being capable of developing a R, of 0.2 to 2.2; continuing the exposure to render the background areas nonpowder receptive (clear the background); applying to said layer a free-flowing powder having a diameter along at least one axis of at least about 0.3 micron but less than about 25 times the thickness of said layer; while said layer is at a temperature below the melting point of the layer and powder particles, physically embedding said powder particles as a monolayer in a stratum at the surface of the powder receptive areas of said layer to yield an image having portions varying in density in proportion to the exposure of each portion; and removing nonernbedded particles from said layer to develop said image.

In a third aspect, this invention is a process for forming deformation images which comprises exposing to actinic radiation in image-receiving manner a solid, negative acting light-sensitive organic layer having a thickness of at least O.l micron, said layer being capable of developing a R,, of 0.2 to 2.2; continuing the exposure to establish a R of 0.2 to 2.2; applying to said layer a free-flowing powder having a diameter along at least one axis of at least about 0.3 micron but less than 25 times the thickness of said organic layer; while the layer is at a temperature below the melting points of the layer and powder particles, physically embedding said powder particles as a monolayer in a stratum at the surface of the powder receptive areas of said light-exposed layer to yield an image having portions varying in density in proportion to the exposure of each portion; and removing nonembedded particles from said organic layer to develop contrast.

In a fourth aspect, this invention is a process for forming direct-reading, positive, continuous-tone deformation images without forming a negative intermediate, which comprises: exposing to actinic radiation in continuous-tone image-receiving manner a solid, positive-acting, light-sensitive organic layer having a thickness of at least 0.1 micron, said layer being capable of developing a R of 0.2 to 2.2; continuing the exposure to clear the background of the light-sensitive layer; applying to said layer of organic material free-flowing powder particles having a diameter along at least one axis of at least about 0.3 micron and less than about 25 times the thickness of said organic layer; while the layer is at a temperature below the melting point of the layer and powder particles, mechanically embedding said powder particles as a monolayer in a stratum at the surface of said light-sensitive layer at ambient temperature'to yield a continuous-tone image having portions varying in density in proportion to the exposure of each portion; and removing nonembedded particles from said organic layer to develop said image.

The present invention provides a method of forming visible deformation images wherein the deformation image is developed by embedding particles of a predetermined size into a stratum at the surface of a powder-receptive, solid, light-sensitive organic layer, This process makes use of the discovery that thin layers of many solid organic materials, some in substantially their naturally occurring or manufactured forms and others including additives to control their powder receptivity and/or sensitivity to actinic radiation, can have surface properties that can be varied within a critical range by exposure to actinic radiation between a particlereceptive condition and a particle-nonreceptive condition such that, by the methods of the present invention, continuous-tone images of high quality can be formed as well as line images and half-tones. As explained below, the particle receptivity and particle nonreceptivity of the solid thin layers are dependent on the size of the particles, the thickness of the solid thin layer and the development conditions, such as layer temperature.

Broadly speaking, the present invention differs from known processes in various subtle and unobvious ways. For example, the particles that form an image are not merely dusted on, but instead are applied against the surface of the light-sensitive thin layer under moderate physical force. The relatively soft or particle-receptive nature of the light-sensitive layer is such that substantially a monolayer of particles, or isolated small agglomerates of a predetermined size, are at least partially embedded in a stratum at the surface of the light-sensitive layer by moderate physical force. The surface condition in the particle-receptive areas is at most only slightly soft but not fluid, as in prior processes. The relatively hard or particle-nonreceptive condition of the light-sensitive surface in the nonimage areas is such that when particles of a predetermined size are appliedvunder the same moderate physical force few, if any,

are embedded sufficiently to resist removal by moderate dislodging action such as blowingair against the surface.

The ease with which continuous-tone images are produced by the process of this invention is significant. In various preferred forms of this invention, the light-sensitive organic layer is sensitized to actinic radiation in such manner that a determinable quantity of actinic radiation changes the surface of the film from the particle receptive condition to the nonreceptive condition. The unexposed areas accept a maximum concentration of particles while fully exposed areas accept no particles. In others, the light-sensitive organic layer is sensitive to actinic radiation in the opposite way, such that a determinable quantity of such radiation changes the surface of the film from the particle nonreceptive condition to the receptive condition. In both types of layers, the sensitivity typically is such that smaller quantities of actinic radiation provide proportionately smaller changes in the surface of the layer to provide a continuous range of particle receptive conditions between fully receptive and nonreceptive conditions. Thus, the desired image may include intermediate light values, as are typically produced by actinic radiation through a continuous tone transparency. While the continuous nature of images produced by the method of this invention cannot be fully explained from a technical standpoint, microscopic studies have established that the range of R (reflection density) obtainable is attributable to the number of particles embedded per unit area. Since only a monolayer of particles is embedded, the light-sensitive layer can be viewed functionally as an ultrafine screen yielding continuous tone images. No such results have been reported in prior powder-imaging methods, even those using some of the same materials but in different modes from those of the present invention. This is probably due to the fact that prior powder-imaging processes rely on electrostatics or liquefaction of the unexposed areas, which lead to the formation of multilayers of powder particles, precluding the formation of continuous tone images.

The quality of the images obtained by the process of this invention is superior to that of prior powder-imaging processes. Line images free of background, having good density and high resolution (better than 40 line pairs per mm.) are readily obtained. As explained below, halftone reproductions and continuous-tone images are also provided readily. Images obtainable by the process of this invention compare favorably with silver halide photographs. Full color reproductions of excellent photographic quality, both halftone and continuous-tone, are provided simply by repeating the basic processes and applying successively suitable powders of cyan, magenta, and yellow hues in any sequence. Black may be added where desired for further detail. Each developed light-sensitive layer can form the substrate for the next light-sensitive layer and particles of a different color can be applied against the surface of each layer.

For use in this invention, the solid, light-sensitive organic layer, which can be an organic material in its naturally occurring or manufactured form or a mixture of said organic material with plasticizers and/or photoactivators for adjusting the powder receptivity and sensitivity to actinic radiation. must be capable of developing a predetermined contrast or R, using a suitable black developing powder under the conditions of development/ The powder-receptive areas of the layer (unexposed areas of a positive-acting, light-sensitive material or the exposed areas of a negative-acting, light-sensitive material) must have a softness such that suitable particles can be embedded into a stratum at the surface of the light-sensitive layer by mild physical forces. However, the layer should be sufficiently hard and nonsticky that film transparencies can be pressed against the surface, as in a vacuum frame, without the surfaces sticking together or being damaged even when heated slightly under high-intensity light radiation. The film should also have a degree of toughness so that it maintains its integrity during development. If the R, of the light-sensitive layer is below about 0.2, the light-sensitive layer is too hard to accept a suitable concentration of powder particles. On the other hand, if the R, is above about 2.2, the light-sensitive layer is so soft that it is difficult to maintain film integrity during physical development and the layer tends to adhere to transparencies precluding the use of vacuum frame exposure equipment. Further, if the R is above 2.2, the light-sensitive layer is so soft that more than one layer of powder particles may be deposited with attendant loss of continuous-tone quality and image fidelity and the layer may be displaced by mechanical forces resulting in distortion or destruction of the image. Accordingly, for use in this invention the light-sensitive layer must be capable of developing a R,, within the range of 0.2 to 2.2 or preferably 0.4 to 2.0 using a suitable black developing powder under the conditions of development.

The R,, of a positive acting light-sensitive layer, which is called R is a photometric measurement of the reflection density of a black-powder-developed light-sensitive layer after a positive-acting, light-sensitive layer has been exposed to sufficient actinic radiation to convert the exposed areas (or most exposed areas, when a continuous-tone transparency is used) into a substantially powder-nonreceptive state (clear the background). The R of a negative acting light-sensitive layer, which is called R is a photometric measurement of the reflection density of a black powder developed area, after a negative-acting, light-sensitive layer has been exposed to sufficient actinic radiation to convert the exposed area into a powder-receptive area.

In somewhat greater detail, the reflection density of a solid, positive-acting, light-sensitive layer (R,,,,) is determined by coating the light-sensitive layer on a white substrate, exposing the light-sensitive layer to sufficient actinic radiation imagewise to clear the background of the solid positive-acting light-sensitive layer, applying a black powder (prepared from 77 percent Pliolite VTL and 23 percent Neo Spectra carbonblack in the manner described below) to the exposed layer, physically embedding said black powder under the conditions of development as a monolayer in a stratum at the surface of said light-sensitive layer and removing the nonembedded particles from said light-sensitive layer. The developed organic layer containing black powder embedded image areas and substantially powder-free nonimage areas is placed in a standard photometer having a scale reading from 0 to 100 percent reflection ofincident light or an equivalent density scale, such as on Model 500 A photometer of the Photovolt Corporation. The instrument is zeroed (0 density; 100 percent reflectance) on a powder-free nonimage area of the light-sensitive organic layer and an average R reading is determined from the powder developed area of line and halftone images. With continuous-tone images the R,, reading is determined on the blackest powder developed area. The reflection density is a measure of the degree of blackness of the developed surface which is relatable to the concentration of particles per unit area. The reflection density of a solid, negative-acting lightsensitive layer (R,,,,) is determined in the same manner except that the negative-acting light-sensitive layer is exposed to sufficient actinic radiation to convert the exposed area into a powder receptive area. If the R under the conditions of development is between 0.2 (63.1 percent reflectance) and 2.2 (0.63 percent reflectance), or preferably between 0.4 (39.8 percent reflectance) and 2.0 (1.0 percent reflectance), the solid, light-sensitive organic material deposited in a layer is suitable for use in this invention.

Although the R,, of all light-sensitive layers is determined by using the aforesaid black developing powder and a white substrate, this invention is not limited to the production of black images or to the use of white substrates. The R, is only a measure of the suitability of a light-sensitive layer for use in this invention.

Since the R,, of any light-sensitive layer is dependent on numerous factors other than the chemical constitution of the light-sensitive layer, the light-sensitive layer is best defined in terms of its R under the development conditions of intended use. The positive-acting, solid, light-sensitive organic layers useful in this invention must be powder receptive in the sense that the aforesaid black developing powder can be embedded as a monoparticle layer into a stratum at the surface of the unexposed layer to yield a R of 0.2 to 2.2 (0.4 to 2.0 preferably) under the predetermined conditions of development and light-sensitive in the sense that upon exposure to actinic radiation the most exposed areas can be converted into the nonparticle receptive state (background cleared) under the predetermined conditions of development. In other words, the positive-acting, light-sensitive layer must contain a certain inherent powder receptivity and light-sensitivity. The positiveacting, light-sensitive layers are apparently converted into the powder-nonreceptive state by a light-catalyzed hardening action, such as photopolymerization, photocross-linking, photooxidation, etc. Some of these photohardening reactions are dependent on the presence of oxygen, such as the photooxidation of internally ethylenically unsaturated acids and esters while others are inhibited by the presence of oxygen, such as those based on the photopolymerization of vinylidene of polyvinylidene monomers alone or together with polymeric materials. The latter require special precautions, such as storage in oxygen-free atmosphere or oxygen-impermeable cover sheets. For this reason, it is preferable to use solid, positive-acting, film-forming, organic materials containing no terminal ethylenic unsaturation.

The negative-acting, solid light-sensitive organic layers useful in this invention must be light-sensitive in the sense that, upon exposure to actinic radiation, the most exposed areas of the light-sensitive layer are converted from a nonpowderreceptive state under the predetermined condition of development to a powder-receptive state under the predetermined conditions of development. In other words, the negative-acting light-sensitive layer must have a certain minimum lightscnsitivity and potential powder receptivity. The negative-acting light-sensitive layers are apparently converted into the powder receptive state by a light-catalyzed softening action, such as photodepolymerization.

In general, the positive-acting, solid, light-sensitive layers useful in this invention comprise a film-forming organic material in its naturally occurring or manufactured form or a mixture of said organic material with plasticizers and/or photoactivators for adjusting powder receptivity and sensitivity to actinic radiation. Suitable positive-acting, film-forming organic materials, which are not inhibited by oxygen, include internally ethylenically unsaturated acids, such as abietic acid, rosin acids, partially hydrogenated rosin acids, such as those sold under the name Staybelite resin, wood rosin, etc., esters of internally ethylenically unsaturated acids, methylol amides of maleated oils such as described in application, Ser. No. 643,367 filed June 5, 1967, now U.S. Pat. No. 3,471,466, phosphatides of the class described in application, Ser. No. 796,841 filed on even date in the name of Hayes, now U.S. Pat. No. 3,585,031, such as soybean lecithin, partially hydrogenated lecithin, dilinolenyl-alpha-leclthin, etc., partially hydrogenated rosin acid esters, such as those sold under the name Staybelite esters, rosin modified alkyds, etc.; polymers of ethylenically unsaturated monomers, such as vinyltoluene alpha methyl styrene copolymers, polyvinyl cinnamate, polyethyl methacrylate, vinyl acetate-vinyl stearate copolymers, polyvinyl pyrrolidone, etc.; coal tar resins, such as coumarone-indene resins, etc.; halogenated hydrocarbons, such as chlorinated waxes, chlorinated polyethylene, etc. Positive-acting, light-sensitive materials, which are inhibited by oxygen include mixtures of polymers, such as polyethylene terephthalate/sebacate, or cellulose acetate or acetate/butyrate, with polyunsaturated vinylidene monomers, such as ethylene glycol diacrylate or dimethacrylate, tetraethylene glycol diacrylate or dimethacrylate, etc.

Although numerous positive-acting, film-forming organic materials have the requisite light-sensitivity and powder receptivity at predetermined development temperatures, it is generally preferable to compound the film-forming organic material with photoactivator(s) and/or plasticizer(s) to impart optimum powder receptivity and light-sensitivity to the lightsensitive layer. In most cases, the light-sensitivity of an element can be increased many fold by incorporation of a suitable photoactivator capable of producing free-radicals, which catalyze the light-sensitive reaction and reduce the amount of photons necessary to yield the desired physical change. For example, the near ultraviolet light sensitivity of soybean lecithin layers can be increased by a factor of 2,000 by the addition of a small concentration of ferric chloride. Whereas it may take 8 minutes to clear the background of a light-sensitive lecithin element devoid of photoactivators using near ultraviolet radiation, lecithin elements containing from about 1-15 percent by weight ferric chloride based on the weight of the lecithin are so light-sensitive that they must be handled under yellow safety lights much like silver halide emulsions. The ferric chloride-photoactivated lecithin is about times slower than silver halide printing papers but faster than commercial diazo material. Ferric chloride also advantageously increases the toughness and integrity of phosphatide layers.

Other suitable photoactivators capable of producing freeradicals include benzil, benzoin, Michlers ketone, diacetyl, phenanthraquinone, p-dimethylaminobenzoin, 7,8- benzoflavone, trinitrofluorenone, desoxybenzoin, 2,3-pentanedione, dibenzylketone, nitroisatin, di( 6-dimethylamino-3- pyradil)methane, metal napthanates, N-methyl-N-Phenylbenzylamine, pyridil, 5-7 dichloroisatin, azodiisobutyronitrile, trinitroanisole, chlorophyll, isatin, bromoisatin, etc. These compounds can be used in a concentration of 0.001 to 2 times the weight of the film-forming organic material (0.1-200 percent the weight of film former). As in most catalytic systems, the best photoactivator and optimum concentration thereof is dependent upon the film-forming organic material. Some photoactivators respond better with one type of film former and may be useful over rather narrow concentration ranges whereas others are useful with substantially all film formers in wide concentration ranges.

The acyloin and vicinal diketonc photoactivators, particularly benzil and bcnzoin are preferred. Benzoin and benzil are effective over wide concentration ranges with substantially all film-forming light-sensitive organic materials. Although slightly inferior to ferric chloride as photoactivators for lecithin, they are capable of increasing the light-sensitivity of the ethanol-insoluble fraction of lecithin to nearly the level of ferric chloride-sensitized lecithin. Benzoin and benzil have the additional advantage that they have a plasticizing or softening effect on film-forming light-sensitive layers, thereby increasing the powder receptivity of the light-sensitive layers. When employed as a photoactivator, benzil should preferably comprise at least 1 percent by weight of the film-forming organic material (0.01 times the film former weight).

Dyes, optical brighteners and light absorbers can be used alone or preferably in conjunction with the aforesaid freeradical producing photoactivators (primary photoactivators) to increase the light-sensitivity of the light-sensitive layers of this invention by converting light rays into light rays of longer lengths. For convenience, these secondary photoactivators (dyes, optical brighteners and light absorbers) are called superphotoactivators. Suitable dyes, optical brighteners and light absorbers include 4-methyl-7-dimethylaminocoumarin, Calcofluor yellow HEB (preparation described in US. Pat. No. 2,415,373), Calcofluor white SB super 30080, Calcofluor, Uvitex W conc., Uvitex TXS conc., Uvitex RS (described in Textil-Rundschau 8 [1953], 339), Uvitex WS conc., Uvitex K, Uvitex CF conc., Uvitex W (described in Tcxtil-Rundschau 8, [1953] 340), Aclarat 8678, Blancophor OS, Tenopol UNPL, MDAC 5-8844, Uvinul 400, Thilflavin TGN conc., Aniline yellowS (low conc. Seto flavine T 5506440, Auramine O, Calcozine yellow OX, Calcofluor RW, Calcofluor GAC, Acetosol yellow 2 RLS-PHF, Eosine bluish, Chinoline yellow-P conc., Ceniline yellow S (high conc.), Anthracene blue Violetfluoresence, Calcofluor white MR, Tenopol PCR, Uvitex GS, Acid-yellow-T-supra, Acetosol yellow 5 GLS, Calcocid OR. Y. Ex. conc., diphenyl brilliant flavine 7 GFF, Resoflorm fluorescent yel. 3 GP], Eosin yellowish, Thiazole fluorescor G, Pyrazalone organe YB-3, and National FD&C yellow. Individual superphotoactivators may respond better with one type of lightsensitive organic film former and photoactivator than with others. Further, some'photoactivators function better with certain classes of brighteners, dyes and light absorbers. For the most part, the most advantageous combinations of these materials and proportions can be determined by simple experimentation.

As indicated above, plasticizers can be used to impart optimum powder receptivity to the light-sensitive layer. With the exception of lecithin, most of the film-forming light-sensitive organic materials useful in this invention are not powderreceptive at room temperature but are powder-receptive above room temperature. Accordingly, it is desirable to add sufficient plasticizer to impart room temperature (15 to 30 C.) or ambient temperature powder receptivity to the lightsensitive layers and/or broaden the R,;,, range of the light-sensitive layers. plasticizers are particularly useful in continuous tone reproduction systems, where the light-sensitive layer must have a R,,,, of at least 0.5 and preferably 0.7-2.0. If the R,,,, is less than 0.5., the developed image lacks the tonal contrast necessary for aesthetically pleasing continuous tone reproductions.

While various softening agents, such as dimethyl siloxanes, glycerol, vegetable oils, etc., can be used as plasticizers, benzil and benzoin are preferred since, as pointed out above, these materials have the additional advantage that they increase the light-sensitivity of the film-forming organic materials. As plasticizer-photoactivators, benzoin and benzil are preferably used in a concentration of l to percent by weight of the film-fonning solid organic material.

The preferred positive-acting light-sensitive film formers containing no conjugated terminal ethyleni'c unsaturation include the esters and acids of internally ethylenically unsaturated acids, particularly the phosphatides, rosin acids, partially hydrogenated rosin acids and the partially hydrogenated rosin esters. These materials, when compounded with suitable photoactivators, preferably acyloins or vicinal diketones together with superphotoactivators, or ferric chloride in the case of lecithin, require less than 2 minutes exposure to clear the background of light-sensitive layers and yield excellent continuous-tone reproductions having a R of at least 0.5 as well as line image and halftone reproductions.

In general, the negative-acting light-sensitive layers useful in this invention comprise a film-forming organic material in its naturally occurring or manufactured form, or a mixture of said organic material with plasticizers and/or photoactivators for adjusting powder receptivity and sensitivity to actinic radiation. Suitable negative acting film-forming organic materials include n-benzyl linoleamide, dilinoleyl-alpha-lecithin, castor wax (glycerol l2-hydroxy-stearate), polyisobutylene, polyvinyl stearate, etc. Of these, castor wax is preferred. These materials can be compounded with plasticizers and/or photoactivators in the same manner as the positive acting light-sensitive film-forming organic materials.

Surprisingly, some solid light-sensitive organic film formers can be used to prepare either positive or negative acting light sensitive layers. For example, a poly(n-butyl methacrylate) layer containing 20 percent benzoin (20 parts by weight benzoin per l00 parts by weight polymer) yields good positive-acting images. Increasing the benzoin level to percent converts the poly(n-butyl methacrylate) layer into a good negative-acting system.

The light-sensitive elements useful in this invention are prepared by applying a thin layer of solid light-sensitive filmforming organic material capable of developing a R,,,, or R of 0.2 to 2.2 to a suitable substrate (glass, metal, ceramic, paper, plastic, etc.) by any suitable means dictated by the nature of the material (hot-melt draw down, spray, roller coating or air knife, flow or dip coating from solvent solution, curtain coating, etc.) so as to produce a reasonably smooth homogeneous layer of from about 0.1- to 40-microns-thick. The light-sensitive layer, must be atleast 0.1 -micron-tl 1ick and preferably at least 0.4 micron in order to hold suitable powders during development. If the light-sensitive layer is less than 0.1 micron, or the developing powder diameter is more than 25 times layer thickness, the light-sensitive layer does not hold powder with the tenacity necessary to form a permanent record. In general, as layer thickness increases, the light-sensitive layer is capable of holding large particles. However, as the light-sensitive layer thickness increases, it becomes increasingly difficult to maintain film integrity during development. Accordingly, the light-sensitive layer must be from 0.1 to 40 microns, preferably from 0.4 to microns, with 0.5 to 2.5 microns being best.

The preferred method of forming light-sensitive elements of predetermined thickness entails flow coating a solution in organic solvent (hydrocarbon, such as hexane, heptane, benzene, etc.; halogenated hydrocarbon, such as chloroform, carbon tetrachloride, l, I I ,-trichloroethane, trichloroethylene, etc.;) of the light-sensitive organic film former alone or together with dissolved or suspended photoactivators and/or plasticizers onto the substrate. Typically, the solution dries in air to a continuous clear film in less than I minute. As illustrated in the examples, the thickness of the light-sensitive layer can be varied as a function of the concentration of the solids dissolved in the solvent.

The substrates for the light-sensitive elements should be smooth and uniform in order to facilitate obtaining a smooth coating. While transparent supports can be employed, opaque supports, preferably white, are preferred for optimum eye appeal and/or for determining R, of a light-sensitive element. Suitable opaque white supports include 80-pound white Lustercoat cover CIS (coated on one side) (S. D. Warren Company, Boston, Mass), Tedlar PVF (polyvinyl fluoride) film, etc. In some cases, it is desirable to apply a hydrophilic subbing layer to substrates, particularly paper substrates. The hydrophilic subbing layer slows down the penetration of organic solvent solutions and, other things being equal, permits the formation of thicker light-sensitive layers. Suitable hydrophilic subbing layers include polyvinyl alcohol, hardened gelatin, polyvinyl pyrrolidone, amylose, polyacrylic acid, etc. The hydrophilic layer has the additional advantage that it can be used as a dye-imbibition receiving layer, as explained below.

A latent image is formed in the light-sensitive elements of this invention by exposing the element to actinic radiation in image-receiving manner for a time sufficient to clear the background of the positive-acting, light-sensitive layers or establish a potential R,,,, of 0.2 to 2.2 with negative-acting, light-sensitive layers. The light-sensitive elements can be exposed to actinic light through a photographic positive or negative, which may be line, halftone or continuous tone, etc.

As indicated, the latent images are produced from positiveacting, light-sensitive layers by exposing the element in imagereceiving manner for a time sufficient to clear the background, i.e., render the exposed areas nonpowder receptive. As explained below, the amount of actinic radiation necessary to clear the background varies to some extent with developer powder size and development conditions. Due to these variations, it is often desirable to slightly overexpose line and halftone images in order to assure complete clearing of the background. Slightly more care is necessary in continuoustone work since overexposure tends to decrease the tonal range of the developed image. In general, overexposure is preferred with negative-acting, light-sensitive elements in order to provide maximum contrast.

After the light-sensitive element is exposed to actinic radiation for a time sufiicient to clear the background of a positiveacting light-sensitive layer or establish a potential R of 0.2 to 2.2, a suitable developing powder having a diameter or dimension along one axis of at least 0.3 micron is applied physically with a suitable force, preferably mechanically, to embed the powder in the light-sensitive layer. The developing powder can be virtually any shape, such as spherical, acicular, platelets, etc. Suitable developing powders include nickel flakes, aluminum flakes, molybdenum disulfide, glass beads, microthene polyethylene, Teflon spheres, montan wax, sulfur, stainless steel spheres, rice starch, pigments, solid dyes, etc., having a diameter along at least one axis of at least 0.3 micron.

Although the developing powder can be a pigment or dye of suitable size, it is preferable to employ resinous or polymeric materials as carriers for pigments or dyes, since most pigments or dyes are not available in the required size range for use in this invention. The pigments or dyes can be ball milled with polymeric carrier in order to coat the carrier with pigment or dye or, if desired, pigments or dyes can be blended above the melting point of a resinous carrier, ground to a suitable size and classified. In some cases, it is advantageous to dissolve dye and carrier in a mutual solvent, dry and grind to suitable size. The black developing powder for determining the R, of a light-sensitive layer and developing black images is formed by heating about 77 percent Pliolite VTL (vinyltoluene-butadiene copolymer) and 23 percent Neo Spectra carbon-black at a temperature above the melting point of the resinous carrier, blending on a rubber mill for 15 minutes and then grinding in a Mikro-atomizer. Commercially available powders such as XEROX 914 Toner give substantially similar results although tending towards slightly lower R, values.

The developing powders useful in this invention contain particles having a diameter or dimension along at least one axis from 0.3 to 40 microns, preferably from 0.5 to 10 microns with powders of the order of l to 7 microns being best for light-sensitive layers of 0.4 to 10 microns. Maximum particle size is dependent on the thickness of light-sensitive layer while minimum particle size is independent of layer thickness. Electron microscope studies have shown that developing powders having a diameter 25 times the thickness of the light-sensitive layer cannot be permanently embedded in light-sensitive layers and, generally speaking, best results are obtained where the diameter of the powder particle is less than about l0 times the thickness of the light-sensitive layer. For the most part, particles over 40 microns are not detrimental to image development provided the developing powder contains a reasonable concentration of powder particles under 40 microns, which are less than 25 times, and preferably less than 10 times, the light-sensitive layer thickness. However, other things being equal, the larger the developer powder particles (above 10 microns), the lower the R,, of the developed image. For example, when XEROX 914 Toner, classified to contain (a) all particles under I micron, (b) I to 3 micron particles, (c) 3 to 10 micron particles, ((1) 10 to 18 microns-and (c) all particles over 18 microns, was used to develop positive acting l-micron-thick lecithin light-sensitive elements after the same exposure, the images had a R of(a) 0.83, (b) 0.95, (c) 0.97, (d) 0.32, and (e) 0.24, respectively.

Although particles over 40 microns are not detrimental to image development, the presence of particles under 0.3- micron diameter along all axes can be detrimental to proper image formation. In general, it is preferable to employ developing powders having substantially all powders having a diameter along at least one axis not less than 0.3 micron, preferably more than 0.5 micron, since particles less than 0.3 micron tend to embed in nonimage areas. For example, mechanical development with commercial carbon-blacks: 0.008 micron Neo Spectra Mark I, 0.020 micron Peerless, 0.025 micron Raven Bead, 0.041 micron Statex B, 0.055 micron Statex R and 0.073 micron Molacco all resulted in substantially equal powder embedment in image and nonimage areas with a positiveacting light-sensitive lecithin element. Substantially less background or nonimage area powder embedment occurred using 0.3-0.4-micron iron oxide IRM-35 I, 0.4-micron iron oxide BK247 and BK-250, 0.55X0.08-micron iron oxide IRN and O.50X0.08-micron IRN I 10 with the same positive-acting, light-sensitive lecithin element. I

As the particle size of the smallest powder in the developer increases, less exposure to actinic radiation is required to clear the background. For example, when XEROX 914 Toner, classified to contain (a) all particles under 1 micron, (b) l to 3 micron particles, (c) 3 to 10 micron particles, (d) 10 to 18 micron particles and (e) over 18 micron particles, was used to develop the light-exposed portions of positive-acting lmicron-thick lecithin light-sensitive elements, the exposed portions had a R of (a) 0.26, (b) 0.23, (c) 0.0, (d) O and (e) after equal exposures. By suitably increasing the exposure time, the R,,,, of the nonimage areas was reduced to substantially zero with particles (21), (b) and (c).

In general, somewhat more deposition of powder particles into nonimage areas can be tolerated when using a black developing powder than a colored powder, since the human eye is less offended by gray background or nonimage areas than by the deposition of colored particles in nonimage areas. Therefore, the concentration of particles under 0.3 micron and the size of the developing powder is more critical when using a colored powder such as cyan, magenta or yellow. For best results, the developing powder should have substantially all particles (at least 95 percent by weight) over 1 micron in diameter along one axis and preferably from i to 7 microns for use with light-sensitive layers of from 0.4 to 10 microns. in this way, powder embedment in image areas is maximum and relatively little powder is embedded into nonimage areas. Accordingly, rice starch granules, which are 5 to 6 microns, are particularly useful as carriers for dyes of different hues.

in somewhat greater detail, the developing powder is applied directly to the light-sensitive layer, while the powderreceptive areas of said layer are in at most only a slightly soft deform able condition and said layer is at a temperature below the melting point of the layer and powder. The powder is distributed over the area to be developed and physically embedded into the stratum at the surface of the light-sensitive layer, preferably mechanically by force having a lateral component, such as to-and-fro and/or circular rubbing or scrubbingaction using a soft pad, fine brush or even an inflated balloon. If desired, the powder may be applied separately or contained in the pad or brush. The quantity of powder is not critical provided there is an excess available beyond that required for full development of the area, as the development seems to depend primarily on particle-to-particle interaction rather than brush-to-surface or pad-to-surface forces to embed a layer of powder particles substantially one-particlethick (monparticle layer) into a stratum at the surface of the light-sensitive layer. When viewed under an inverse microscope, spherical powder particles under about 10 microns in diameter enter the powder-receptive areas first and stop dead, embedded substantially as a monolayer. The larger particles seem to travel over the embedded smaller particles which do not rotate or move as a pad or brush is moved back and forth over the developed area. Nonspherical particles, such as platelets, develop like the spherical powders except that the flat side tends to embed. Only a single stratum of powder particles penetrates into the powder-receptive areas of the light-sensitive layer even if the light-sensitive layer is several times thicker than the developer particle diameter.

The minimum amount of powder of the preferred type required to develop an area to its maximum density is about 0.01 gram per square inch of light-sensitive surface. Ten to or more times this minimum range can be used with substantially the same results, a useful range being about 0.02 to 0.2 gram per square inch.

The pad or brush used for development is critical only to the extent that it should not be so stiff as to scratch or scar the film surface when used with moderate pressure with the preferred amount of powder to develop the film. Ordinary absorbent cotton loosely compressed into a pad about the size of a baseball and weighing about 3 to 6 grams is especially suitable. The developing motion and force applied to the pad during development is not critical. A force as low as a few grams ap plied to the pad when using the preferred amount of powder will develop an area of the film to essentially maximum density, although a suitable material could withstand a developing force of 300 gramswith'substantially the same density resulting in both instances. A force of 10 to grams is preferred to assure uniformity of results. A slightly longer developing time (30 seconds) may be required at the lower loading while only a few seconds would be required at the higher loading. The speed of the swabbing action also is not critical other than that it affects the time required; rapid movement requiring less time than slow. The preferred mechanical action involved is essentially the lateral action applied in ultrafine finishing of a wood surface by hand sanding or steel wooling.

Hand swabbing is entirely satisfactory, and when performed under the conditions described above, will reproducibly produce the maximum density which the material is capable of achieving. That is, the maximum concentration of particles per unit area will be deposited under the prescribed conditions, dependent upon physical properties of the material such as softness, resiliency, plasticity, and cohesivity. Substantially the same results can be achieved using a mechanical device for the powder application. A rotating, or rotating and oscillating, cylindrical brush or pad may be used to provide the described brushing action and will produce a substantially similar end result.

if a substantially larger mechanical force is employed to develop positive-acting, light-sensitive layers, the solid, unexposed material together with embedded powder are removed from the substrate surface and moved to the light-exposed nonimages areas forming a reversal image. It has also been found that it is possible to move the unexposed positive-acting light-sensitive layer from a grained metal substrate to the exposed portion prior to powder development. Excellent negative halftone images have been produced by applying developer powder to the originally positive-acting system.

After the powder application, excess powder remains on the surface which has not been sufficiently embedded into, or attached to, the film. This may be removed in any convenient way, as by wiping with a clean pad or brush usually using somewhat more force than employed in mechanical development, by vacuuming, by vibrating, or by air doctoring. For simplicity and uniformity of results, the excess powder usually is blown off using an air gun having an air line pressure of about 20 to 40 psi. The gun is preferably held at an angle of about 30 to 60 to the surface at a distance of l to 12 inches (3 to 8 preferred). The pressure at which the air impinges on the surface is about 0.1 to 3, and preferably about 0.25 to 2, p.p.s.i. Air cleaning may be applied for several seconds or more until no additional loosely held particles are removed. The remaining powder should be sufficiently adherent to resist removal by moderately forceful wiping or other reasonable abrasive action. If a resinous binder is used in the formulation of the developing powder, scuff resistance can be improved after removing excess powder by brief (2 to 5 seconds) exposure of the specimen to heat or to solvent vapors to fuse the resin.

Under some circumstances, it is possible to develop an image without applying mechanical force, such as by using air pressure or cascade-development techniques, which use large carrier beads as a driving force. However, the image is usually imperfect in the sense that it has lower contrast and the image areas lack uniformity or proper tonal values, when compared to images developed using the prescribed mechanical force. For example, when a light-sensitive Staybelite resin element, capable of yielding a R of 1.9 with the aforementioned preferred black toner (77 percent Pliolite VTL-23 percent Neo Spectra carbon-black) at room temperature using mechanical force, was dusted at room temperature with the preferred black toner and subjected to air pressure (a nonmechanical, physical force), such as that normally used to remove excess powder particles from nonimage areas, a nonuniform image was obtained having a maximum R,,,, of 0.67. The nonuniform image was similar to images developed with insufiicient developer using mechanical force. When the nonuniform air-developed element was gently swabbed with a clean cotton pad, image uniformity improved somewhat. When the same light-sensitive Staybelite resin element, capable of yielding a R of 0.99 with XEROX 914 Toner at room temperature using mechanical force, was developed by cascade development at room temperature using XEROX 914 Toner with large carrier beads as a driving force, air cleaned and wiped with a cotton pad, an image having a R of 0.66 was obtained. Although this image lacked the excellent resolution and uniformity of images developed using mechanical force, it had substantially better image qualities than images developed using air pressure alone or air pressure followed by gentle wiping. While air pressure or cascade development have been used with some success with light-sensitive Staybelite resin elements, not all light-sensitive elements of this invention can be developed in this manner. Attempts to develop light-sensitive lecithin elements using air pressure or cascade development at room temperature have generally resulted in images having a R ofless than 0.2.

The reflection density, and the R,,,, in particular, ofa lightsensitive layer is also dependent upon the temperature of the light-sensitive layer during physical embedment. In general, the higher the temperature of the light-sensitive layer, the higher the R,,,, of the developed image. For example, Staybelite Ester No. 10 alone, which is incapable of forming an image having a R,,,, of a least 0.2 from 130 F., can be developed to 21 R of about 0.2 at 135 F., and about 0.6 at 165 F. Similarly, soybean lecithin, in its naturally occurring form, which readily develops a R of about 0.7 to 0.9 with a suitable developer at room temperature, yields a R of less than 0.2 at 0 F.

To some extent reproducibility of results and length of exposure are also dependent upon the relative humidity of the development chamber or area. For development at higher relative humidity, sensitized lecithin elements must be exposed to more actinic radiation to clear the background. For example, other things being equal, an exposed lecithin element, which is nonpowder receptive at 38 percent R.H. (relative humidity) has a background R of 0.16 at 48 percent R.H., 0.38 at 56 percent R.H. and 0.61 at 65 percent R.H. On the other hand, rosin derivatives, such as Staybelite Ester No. 10, are much less sensitive to relative humidity.

As indicated above, substrates bearing a hydrophilic subbing layer, such as hardened gelatin, polyvinyl alcohol, polyvinyl pyrrolidone, polyacrylic acid amylose, etc., can be employed as dye-imbibition receiving layers. In this modification, a suitable solid, positive-acting or negative-acting light-sensitive layer is applied to the hydrophilic subbing layer, exposed to actinic radiation in image-receiving manner to form a latent image in the manner described above and developed with polymeric developer particles of at least 0.3 micron along at least one axis containing a hydrophilic dye. The polymeric developer particles are prepared in the manner described above by mixing a hydrophilic dye with a suitable polymeric carrier, such as polyvinyl alcohol, rice starch granules, butadiene-vinyltoluene copolymer, etc., or by melting resinous carrier and hydrophilic dye and grinding to the desired size. An aesthetically more pleasing monochromatic image is then produced by treating the developed image with vapors of a liquid solvent for the dye which transfers the previously particularly dispersed dye to the subbing layer in molecularly dispersed form. For example, if the dye is water-soluble, it can be transferred to the subbing layer by steam. This technique is ideally suited to the production of excellent monochromatic continuous-tone images. Essentially the same results can be obtained using a hydrophobic subbing layer, such as polystyrene or polyvinylidene chloride, ahydrophobic dye and suitable solvent vapors.

The following examples are merely illustrative and should not be construed as limiting the scope of this invention.

EXAMPLE l One gram Staybelite Ester No. (partially hydrogenated rosin ester of transparency0.22 grams benzil and 0.30 grams 4-methyl-7-dimethylamino-coumarin, dissolved in 100 millimeters Chlorothene (l,l,l,-trichloroethane) was applied to the gelatin side of an I lXl4 hardened gelatin-coated paper by flowing the solution over the substrate supported at about a 60 angle with the horizontal. After air drying for approximately 1 minute, the light-sensitive layer was approximately 2.0 to 2.25-microns-thick. The light-sensitive layer was placed in a vacuum frame in contact with five representative transparencies, as identified below. After exposure to a mercury point light source for about 60 seconds, the exposed light-sensitive element was removed from the vacuum frame and developed in a room maintained at 75 F and 37 percent relative humidity by rubbing a cotton pad containing approximately 5 grams of a 77 percent by weight Pliolite VTL (vinyltoluene-butadiene copolymer) and 23 percent Neo Spectra carbon-black toner, prepared in the manner described below across the element. The black developing powder was embedded into the unexposed areas of the light-sensitive layer by rubbing the lightly compressed absorbent cottonvpad about the size of a baseball weighing about 3 to 6 grams back and forth over the light-sensitive layer using essentially the same force used in ultrafine finishing of wood surface by hand sanding or steel wooling. The excess powder was removed from the light-sensitive layer by impinging air at an angle of about 30 to the surface until the surface was substantially free of unembedded particles. The reproduction was then wiped with a fresh cotton pad resulting in excellent resolution and faithful reproduction of the transparencies. The scanning electron microscope showed that a monolayer of particles was embedded in the image areas. The developed reproduction was then placed in a chamber containing trichloroethylene vapors maintained at room temperature for about 5 seconds to fuse the powder particles to the light-sensitive layer.

The transparencies used in this example included (1 a 133- line-per-inch halftone transparency containing boxes A to H and J to M, whose light transmission varies from 9.7 percent to 85.1 percent, located across the top of the light-sensitive element, (2) an -line-per-inch positive halftone transparency of a young girl positioned to the left under the l33-line-perinch halftone transparency, (3) a Stouffer No. 1 continuoustone resolution guide bearing steps numbered from 1 to 21 positioned the right under the l33-line-per-inch halftone transparency, (4) a l20-line-per-inch halftone and 6-to-l0- point type positive transparency in the lower left-hand corner and (5) a continuous-tone positive transparency of a womans head and shoulders in the lower right-hand comer.

The percent light transmission of the halftone areas of the l33-line-per-inch halftone transparency and R,, of the developed halftone areas are set forth below in table I.

The percent light transmission of the Stouffer No. 1 continuous-tone resolution guide and R,, of the developed image areas are set forth below in table II.

TABLE II Light Rcflectiom Transmission Density Numbered Steps ofTranspar-ency of Reproduction I 93.3 0.00 2 61.7 0.01 3 43.6 0.03 4 28.2 0.21 5 19.9 0.54 6 14.4 0.89 7 10.9 1.15 8 8.3 L4] 9 6.3 L70 [0 4.3 1.85 l l 2.9 1.92 [2 2.1 2.00 l3-2l LBS-0.10 2.00

The R of the developed continuous-tone reproduction of the woman ranged from 0.08 in the forehead area to L2 in the shadow tone.

The black developing powder used in the example and employed for determining the R,, of light-sensitive layers as prepared by heating a mixture of about 77 percent by weight Pliolite VTL (vinyltoluene-butadiene copolymer) and 23 percent by weight Neo Spectra carbon-black to 350 F., to produce a pliable mixture, mixing on a rubber mill for 15 minutes, cooling to room temperature and the grinding in a Mikro-atomizer. Over 99 percent by weight of the particles in the toner were between about 2 to 40 microns as measured by a Coulter Counter. Approximately 28 percent by weight of the powder particles were from about 2 to microns with an additional 22 percent by weight from 10 to microns.

The above example clearly shows that excellent continuoustone, halftone and line images can be produced by the method of this invention.

EXAMPLE ll Example I was repeated using a 90 second exposure and developed with (l) Statex B carbon-black having an 0.04l micron average particle size in place of the Pliolite VTL-carbon black toner and (2) black iron oxide lRN-35l having a 0.3 to 0.4 micron average particle size in place of the Pliolite VTL-carbon-black toner.

The Statex B carbon-black embedded into both image and nonimage areas resulting in dark-black images on a black background. The dots in the l33-line-per-inch halftone could not be distinguished with the naked eye due to the dark background. In some cases, the shadow tones (halftone boxes A to G) were visible since they developed blacker or shinier than the background areas while in other cases the most exposed areas (face of the woman prepared from the continuous-tone positive) was apparent only by virtue of the higher gloss in the most light-exposed areas as compared to a duller black in the least exposed areas. The Stoufier resolution guide gave additional anomalous results with steps I to 3 having essentially the same blackness as the background areas, steps 4 to 6 a very dark appearance due to the high gloss in these steps and steps 7 to 2l having a duller black than steps 4 to 6.

For the most part, the black iron oxide was embedded almost solely into the unexposed areas. Although the light-irradiated background areas had a light-gray cast, it was possible to distinguish the individual dots in each of boxes A to H and J to M of the l33-line-per-inch halftone. Seven steps on the Stouffer chart were distinguishable with the naked eye. The continuous-tone image of the woman did not develop properly since the length of exposure was insufficient to harden the light-exposed areas sufficiently to resist embedment of particles of this small size. If exposed for a longer length of time a continuous-tone reproduction is formed.

The above example clearly shows that particles having a diameter along at least one axis of at least 0.3 micron are suitable for use in this invention.

EXAMPLE Ill Five grams of the ethanol-insoluble fraction of soybean lecithin, 1.5 grams benzil and 0.05 grams 4-methyl-7- dimethylaminocoumarin, dissolved in ml. C C1. was flow coated over Lustercoat paper and air dried to form a Li micron light-sensitive layer. The light-sensitive element was used to copy a translucent engineering drawing by passing the light-sensitive element through a Bruning copyflex Model 250 at No. 10 setting equipped with a mercury lamp rated at I00 watts per inch. At this speed setting which is normally used for medium speed diazos, the exposure time was about 5 to 6 seconds. An excellent black and white copy was formed embedding the Pliolite VTL-Neo Spectra carbon-black toner described in example I in the manner described in example I.

The light-sensitive element described in this example formed excellent continuous-tone reproductions by l exposing through a continuous-tone positive for 2% minutes using a sunlamp as the light source and (2) exposing through a continuous-tone positive for 30 seconds using a sunlamp as the light source, followed by heating the exposed element in an oven at C., for 3 minutes and cooling to room temperature prior to powder embedment.

EXAMPLE IV This example illustrates the use of the light-sensitive element of example III in a complex lens system. Line subjects were reproduced using the light emitted from a 750-watt projector. The light was projected through a slide transparency through a lens onto a mirror about 3 feet in front of the projector that reflected the image downward about 2 feet focusing on the lecithin-coated light-sensitive layer. After exposure for about 5 minutes and heating at 150 C., in an oven for 4 minutes and cooling to room temperature, an excellent line image was formed using the developer powder described in example I in the manner described in example 1.

EXAMPLE V Five grams of the ethanol-insoluble fraction of soybean lecithin and 0.2 grams benzil, dissolved in l00 ml. carbon tetrachloride was flow coated over Lustercoat paper and air dried. The light-sensitive element was used to reproduce a continuous-tone image from a continuous-tone transparency by passing the light-sensitive element through the Bruning Copyflex copier described in example III at No. 3 speed setting. At this speed setting, which is normally used for slowspeed diazos, the exposure time was about 25 seconds. An excellent continuous-tone black and white reproduction was formed by embedding the Pliolite VTL-Neo Spectra carbonblack toner described in example I in the manner described in example 1.

EXAMPLE V! This example illustrates the production of an engineering drawing using the Bruning Copyflex copier described in example ill at its fastest setting. Twenty grams of unfractionated, substantially oil-free soybean lecithin and 2gra'rns ferric chloride in 200 ml. carbon tetrachloride were mixed for 30 seconds with ultrasonic agitation, centrifugal and 100 ml. decanted. A portion of the decanted liquid was flow coated on Lustercoat paper in the manner described in example "I. The light-sensitive element was used to copy a translucent engineering drawing by passing the light-sensitive element through the Bruning Copyflex copier at No. 40 setting. At this speed setting, exposure time was about 1 second. An excellent, slightly overexposed black and white copy was formed by embedding the Pliolite VTL-Nee Spectra carbon-black toner in the manner described in'exarnple Ill. The reproductionwas EXAMPLE V11 Five grams of unfractionated, substantially oil-free soybean lecithin and 0.5 grams ferric chloride in 100 ml. Chlorothene was dispersed by an ultrasonic tool for 1 minute, filtered through Celite Super cell and flow coated on Lustercoat paper in the manner described in example III. An image was projected on the light-sensitive element by placing the National Bureau of Standards microcopy resolution chart slide in a 35 ml. projector equipped with a 500 -watt projection bulb. The image was projected onto the lecithin coated paper for 90 seconds and developed with XEROX 914 Toner to yield an excellent enlargement 7 times that of the original.

When the National Bureau of Standards transparency was placed in contact with the light-sensitive lecithin element on a glass plate and exposed to an arc lamp for 30 seconds, an excellent contact print resolving 60 line pairs per mm., was developed with XEROX Toner.

EXAMPLE VIII This example illustrates the use of the light-sensitive element of example VII in the production of reflex copies, The light-sensitive element of example VII was placed in contact with a printed page with the printed side in contactwith the light-sensitive lecithin layer. The backside of the light-sensitive element was exposed to a fluorescent lamp for approximately 1 minute. The image was developed in the manner described in example III yielding an excellent mirror line image.

EXAMPLE IX This example illustrates that the thickness of flow-coated light-sensitive layers of this invention can be controlled by controlling the solids in the light-sensitive coating since layer thickness increases as total solids in the coating composition increases.

Six hundred-twenty-five-one thousandths of a gram of Stabelite resin (partially hydrogenated rosin acids), 0.05 gram benzil and 0.156 gram 4-methyl-7-dimethylaminocoumarin, dissolved in 100 ml. Chlorothene was applied to the gelatin side of hardened gelatin-coated paper, to aluminum foil and to gelatimcoated glass by flowing the solution over the substrate supported at about a 60 angle with the horizontal. The thickness of the light-sensitive coatings was determined by weight difference (weighing the substrate before and after coating) or by sectioning the central portion of the coated light-sensitive element. The light-sensitive layer was 0.55 micron on gelatin-coated glass by sectioning, 0.59 micron on gelatin-coated glass by weight difference, 0.65 micron on aluminum foil by weight difference and 0.75 micron on the gelatin-coated paper by sectioning.

One and one-quarter grams Staybelite resin, 0.1 gram benzil and 0.3125 gram 4-methyl-7-dimethylaminocoumarin, dissolved in 100 ml. Chlorothene was applied to aluminum foil in the above described manner and yielded a 2.25 micron lightsensitive layer by weight difference. Two and one-half grams Staybelite resin, 0.2 gram benzil and 0.625 gram 4-methyl-7- dimethyl-aminocoumarin, dissolved in 100 ml. Chlorothene was flow coated on hardened gelatin coated paper yielding a 4.3 micron light-sensitive layer by sectioning.

Five grams Staybelite resin, 0.4 gram benzil and 1.25 grams 4-methyl-7-dimethylamlnocoumarin, dissolved in 100 ml. Chlorothene was flow coated on aluminum foil and on steel foil. The light-sensitive layer was 6.25 micron by weight difference on aluminum foil and 6.04 microns by sectioning on steel foil.

Each of the light-sensitive layers was exposed to light through a positive continuous-tone transparency and developed with the developing powder of example I in the manner described therein to yield excellent positive continuous-tone images.

EXAMPLE X EXAMPLE XI One and one-fourth grams Staybelite resin F (partially hydrogenated rosin acids), 0.1 gram benzil and 0.3125 gram 4-methyl-7-dimethylaminocoumarin, dissolved in 100 ml. Chlorothene was flow coated on the gelatin side of hardened gelatin-coated paper, exposed to a fluorescent lamp through a continuous-tone positive transparency and developed in the manner described in example I to form an excellent continuous-tone positive reproduction.

EXAMPLE XII One and one-fourth grams wood rosin, 0.15 gram benzil and 0.3125 gram 4-methyl-7-dimethylaminocoumarin, dissolved in 100 ml. Chlorothene was flow coated on the gelatin side of hardened gelatin-coated paper, exposed to a fluorescent lamp through a continuous-tone positive transparency and developed in the manner described in example 1 to form an excellent continuous-tone positive reproduction.

EXAMPLE XIII One and one-fourth grams abietic acid, 0.15 gram benzil and 0.3125 gram 4-methyl-7-dimethylaminocoumarin, dissolved in 100 ml. Chlorothene was flow coated on the gelatin side of a hardened gelatin-coated pap-er, exposed to a fluorescent lamp through a continuous-tone positive and developed in the manner described in example I to yield an excellent continuous-tone positive reproduction.

EXAMPLE XIV This example illustrates the preparation of continuous-tone and halftone reproductions using a negative-acting light-sensitive material of this invention. Eight-tenths gram Castorwax F-l (hydrogenated castor oil), 0.2 gram benzil and 0.2 gram 4-methy1-7-dimethylaminocoumarin, dissolved in 100 ml. Chlorothene was flow coated on the gelatin side of a hardened gelatin-coated paper. The light-sensitive layer was placed in a vacuum frame in contact with continuous-tone negatives and an -line-per-inch negative halftone transparency. After exposure to a -ampere carbon arc lamp for approximately 80 seconds, the exposed light-sensitive element was developed with the black developing powder, in the manner described in example I to form continuous-tone positive and halftone positive of the respective negative transparencies. The developed reproductions were then placed in a chamber containing trichloroethylene vapors maintained at room temperature for about 5 seconds to fuse the powder particles to the light-sensitive layer.

EXAMPLE Xv One and one-quarter grams Chlorowax (chlorinated paraffin) 70 LMP, 0.3 gram benzil and 0.3125 gram 4-methyl-7- dimethylaminocoumarin, dissolved in 100 ml. Chlorothene was flow coated on the gelatin side of a hardened gelatin coated paper, exposed to light through a continuous-tone positive transparency and developed in the manner described in example I with the Pliolite VTL Neo Spectra carbon-black toner to form an excellent continuous-tone positive reproduction. This sensitized system is roughly equivalent to various rosin esters, acids and hydrogenated rosin acids and esters.

Five grams of Piccotex (alpha-methyl styrene-vinyltoluene copolymer having a ball and ring softening print of 75C.) and 1 gram benzil, dissolved in 100 ml. Chlorothene was flowcoated on a grained aluminum plate The light-sensitive layer was placed in a vacuum frame in contact with a continuoustone positive transparency, an 85-line-per-inch positive halftone transparency and positive line transparency. After exposure for minutes to a 100 ampere arc lamp at a distance of 48 inches, the light-sensitive element was developed with the Pliolite VTL-carbon-black toner in the manner described in example I to form positive continuous, halftone and line reproductions. The light source was maintained at 48 inches in order to avoid heating the light-sensitive layer which tends to become too tacky when warmed slightly.

EXAMPLE XVII Seven grams Cumar V1 (para-coumarone-indene resin), 3 grams l-lercolyn D (hydrogenated methyl ester of rosin), 3 grams benzil and 1 gram 4-rnethyl-'I-dimethylaminocoumarin was flow coated on a grained aluminum plate. The light-sensitive layer was placed in contact with a continuous-tone positive transparency. After exposure to a sunlamp for about 5 minutes, the exposed light-sensitive element was developed in the manner described in example I to form a continuous-tone positive image.

EXAMPLE XVIII This example illustrates an attempt to use the polymerizable composition described in Example I of US. Pat. No. 3,060,024 in the manner described in example I of said patent and in accordance with the present invention. An initial preparation of polyethylene terephthalate/sebacate was prepared using a procedure based on that described by Sorenson and Campbell in Preparation Methods of Polymer Chemistry, Interscience Publishers, Inc., New York (1961) pp. 1 [3-4 for the preparation of polyethylene terephthalate. Fifteen grams (0.08 mole) of dimethyl terephthalate, 18 grams (0.08 m) dimethyl sebacate, 24grams (0.39 m) ethylene glycol, 0.05 gram calcium acetate hydrate, and 0.12 gram of antimony trioxide were placed in a flask. The flask was immersed and kept for 3 hours in a 197 C., metal bath while a slow stream of nitrogen was passed through a capillary tube which reached to the bottom of the flask. The bath temperature was raised to 222 C., for 20 minutes and then to 283 C., for 2 hours. The nitrogen flow was discontinued at this point. The polymerization was continued for five hours at about 0.3 mm., pressure. The resulting product had the consistency of a thick syrup. A coating solution was prepared according to example I of the patent containing grams polyethylene terephthalate/sebacate, 83.3 cc. dichloromethane, 2.7 grams tetraethylene glycol diacrylate, 0.003 gram phenanthraquinone and 0.003 gram p-methoxyphenol. This coating solution was quite fluid and was flow coated on a 3-mil Mylar substrate yielding a layer between 0.5 and 1 mil which was very soft and greasy. The coatings were much too soft to place contact with transparencies in a vacuum frame.

A coating on 3-mil Mylar was exposed to ultraviolet light through a metal stencil mask held out of contact from the coating for a prolonged period and heated on a hotplate at 120 C. resulting in liquefaction of the unexposed areas. Five micron aluminum powder platelets having a diameter along one axis of from 0.8 to 15 microns was dusted over the surface and the specimen was allowed to cool. The aluminum powder was wiped off the light-irradiated areas leaving a heavy multilayer deposit of particles frozen into the unexposed areas. Although the polymerizable layer was not as thick as described in example I of the patent, the unexposed material became quite fluid at the dusting-on temperature, and a heavy multilayer deposit of aluminum platelets was obtained.

Since the above light-sensitive layer could not be used in contact with a transparency in a vacuum frame, a second preparation of polyethylene terephthalate/sebacate was made by essentially the same procedure except that 0.l2 mole of dimethyl terephthalate and 0.06 mole of dimethyl sebacate was used. A coating solution was prepared using the polyethylene terephthalate/sebacate as described in example I. A film deposited from this solution on Mylar was dry to the touch. Cotton-swab development of the unexposed layer at room temperature using mechanical force with the same aluminum platelets produced a smooth reflective image, which was substantially a monolayer of the aluminum platelet particles. Although this material was not quite as fluid at C. as the product made with the first batch of polyethylene terephthalate/sebacate, dusting-on at i20 C. resulted in a rough multilayer deposit. Attempts to image this light-sensitive element in a vacuum frame using an arc lamp gave only a faint hint of where the transparency had been but no recognizable image.

A continuous-tone reproduction was produced with the light-sensitive composition described in the preceding paragraph by adding 20 percent by weight benzil to the coating composition based on the weight of the polyethylene terephthalate/sebacate. The composition was flow coated onto grained aluminum, placed in contact with a continuoustone positive and exposed to a sunlamp for l5 minutes. The light-sensitive element was developed with mechanical force using titanium dioxide in the manner described in example I yielding a continuous-tone positive image which was inferior to those described in the preceding examples. Heating the plate to 120 C. prior to development and dusting on'titanium dioxide destroyed the continuous tone effect.

EXAMPLE XIX A coating solution was prepared according to example I of US. Pat. No. 3,060,024 using polyethylene terephthalate/sebacate (prepared from 0.12 mole dimethyl terephthalate and 0.06 mole dimethyl sebacate), 1.5 grams benzil, and 0.0l gram 4-methyl-7-dimethylarninocoumarin was flowcoated on grained aluminum and air dried. Two sections of the coated aluminum sheet were similarlyexposed for 15 minutes to sunlamp through the same continuous-tone positive transparency. One light exposed section was placed on a hotplate set at C., titanium dioxide was sprinkled over the entire surface, cooled to room temperature, and excess titanium dioxide removed. The result was a harsh differential between areas of particle retention and particle rejection with no intermediate areas of particle retention corresponding to intermediate degrees of light exposure. The other exposed section was developed with titanium dioxide at room temperature using the prescribed mechanical application of swabbingwith a cotton pad resulting in similar extremes in powder retention to the dusting on technique but also producing the many intermediate degrees of powder receptivity between these extremes in proportion to the degree of light exposure.

EXAMPLE XX This example illustrates how the room temperature reflection density of the methylol amide of example I! of U.S. Pat. No. 3,471,366 varies with the concentration of glycerol in the coating composition. A solution of the methylol amide of example II was applied to a glass substrate. The light-sensitive layer had a R of 0 at room temperature. With the addition of (l) 0.2 gram, (2) 0.4 gram, (3 0.6 gram, (4) 0.8 gram, (5) 1.0 gram and (6) 1.2 grams of glycerol per 10 cc. of coating solution, the room temperature R using XEROX 914 Toner was respectivelyfl) 0.8,(2) 1.0, (3) l.5,(4)l.7,( 5) 1.85 and (6) 2.0.These layers were sensitive to uni-same: lightradiation and the background could be cleared by suitable exposure.

EXAMPLEXXJ I gelatin-coated paper, exposed to light through a metal mask for 20 seconds and developed in the manner described in example I using XEROX 914 Toner to form a positive image.

EXAMPLE XXII Five grams poly(n-butylmethacrylate) and Sgrams benzoin, dissolved in 690 ml. methylethyl ketone was flow coated on gelatin-coated paper, exposed to light through a metal mask for 20 seconds and developed in the manner described in example I using XEROX 9I4 Toner to form a negative image.

When this example was repeated using grams poly n-butylmethacrylate and 2.5 grams benzoin dissolved in 375 ml. methylethyl ketone, a positive image was formed.

EXAMPLE XXIII This example illustrates the relationship between the thickness of the light-sensitive layer and diameter of developer particles. A series of lecithin solutions comprising from 0.5 gram to 50 grams of substantially oil-free soybean lecithin in 100 ml. of Chlorothene were flow coated on glass and air dried. The layer thickness was determined by sectioning the glass coated with solutions containing at least 5 grams lecithin and extrapolating the thickness of solutions containing less than 5 grams lecithin. The data is set forth below in table Ill.

Spherical glass beads of known uniform size [(I) 9to 17 microns, (2) I7 to 24 microns, (3) 24 to 26 microns, (4) 26 to 30 microns and (5) 53 to 75 microns] were spread generously over the lecithin elements and a loaded rubber roller was moved over the glass beads in order to embed the particles through particle-to-particle contact. The excess beads were blown off with an air stream in the manner described in example I. Photomicrographs were made of each area at IOO-X magnification. The monoparticles embedment of the glass beads was apparent under each condition for which the beads remained attached to the film. The larger beads remained embedded in the thicker layers only, with the number of beads embedded per unit area being directly proportional to layer thickness; the smaller beads showed the same proportional relationship to layer thickness, but remained attached to the thinner layers.

None of the 53 to 74 micron beads remained embedded in the layers of less than l-micron-thickness although cavities were apparent in the lecithin layer where beads were pressed into the layer but were subsequently blown off by the air. Approximately half the surface of the I micron layer was covered by beads of 9 to 17 microns, a few 17- to 24-micron beads were embedded and only scattered larger beads were embedded, Higher concentration of beads remained in the layers of increasing thickness. The 9 to l7-micron beads and the I7- to 24-micron beads were packed about as closely as possible as a monolayer in the 5- to 6-micron layer. The 24- to 26- micron and 26- to 30rnicron beads were fairly closely packed in the 5- to 6-rnicron layer and approximately half of the 5- to o-micron layer was covered by the 53- to 74-micron beads. The above data clearly shows that the maximum particle size that can be embedded in any layer varies with layer thickness.

EXAMPLE XXIV Granular rice starch, which is uniformly 5 to 6 microns, was applied the soybean lecithin layers of from /ato 5- to 6- microns-thickness described in example XXIII using a cotton pad in the manner described in example I. Rice starch was embedded in negligible amounts in the lfi-micron layer, in scattered areas of the less than 0.25-micron layer, about 50 percent of the more than 0.25-micron layer, about percent of the approximately l-micron layer and closely packed in the 2- and 5- to 6-micron layers. Based on data in examples XXIII and XXIV, the developer particle must have a diameter along one axis less than 25 times the light-sensitive layer thickness in order to be embedded in the light-sensitive layer.

EXAMPLE XXV The light-sensitive soybean lecithin element described in example III was exposed to a sunlamp through a metal mask, developed with stainless steel spheres having a range of from I to 60 microns (number average of I3 microns) using a cotton pad in the manner described in example I to form a positive image.

The same results were obtained using micronized irregular polygonal coke particles of I to 5 microns as the developing powder.

EXAMPLE XX VI This example illustrates the screening of a number of free radical progenitors as photoactivators for light-sensitive lecithin compositions. Five grams of the ethanol insoluble residue of soybean lecithin and from 0.1 to 0.2 grams of free radical progenitor, dissolved in I00 ml. carbon tetrachloride were flow coated on Lustercoat paper in the manner described in example III. A metal mask was positioned over the light-sensitive element and individual areas were exposed for 1,2,4 and 8 minutes. The results are set forth below in table IV. The photoactivators rated A had a pronounced effect on the light-sensitivity of the lecithin layer. Those ranked B made a definite improvement, although not nearly as much under the conditions of evaluation as those rated A. Many of the materials rated C had some effect light-sensitivity but were considerably less effective than those rating A and B.

TABLE IV Sensitizer Rating (70000nnwwmwmm mwwwmmm OOOOGOOOOOOOOOOOO EXAMPLE XXVll This example illustrates the development of colored reproductions using a polymeric material as a carrier for a hydrophilic dye in dye-imbibition imaging. One and onequarter grams Staybelite Ester No. 10, 0.25 gram benzil and 0.25 gram 4-methyl-'I-dimethylaminocoumarin, dissolved in 100 ml. Chlorothene was applied to the gelatin side of a hardened gelatin-coated paper by flow coating the solution over a substrate supported at about a 60 angle with the horizontal. After air drying for approximately 1 minute, the light-sensitive layer was approximately 2.25- to 2.50-micronsthick. The light-sensitive element was placed in a vacuum frame in contact with continuous tone, halftone and line transparencies in the manner described in example 1 and exposed to a carbon arc for about 60 seconds. The light-sensitive element was removed from the vacuum frame and developed in a room maintained at 75 F. and 37 percent relative humidity by rubbing a cotton pad containing an Alphazurine 2G (cyan) polyvinyl alcohol toner of from 1- to l-microns-diameter along the largest axis, prepared in the manner described below, across the element. The cyan developing powder was embedded into the unexposed areas of the light-sensitive layer by rubbing the loosely compressed absorbent cotton pad about the size of a baseball weighing about 3 to 6 grams back and forth over the light'sensitive layer using essentially the same force used in ultrafine finishing of wood surfaces by sanding or steel wooling. The excess powder was removed from the light-sensitive layer by impinging air at an angle of about 30 to the surface until the surface was substantially free of particlesr'lhe reproduction was then wiped with a fresh cotton pad resultingin excellent continuous tone, halftone and line reproductions of the positive transparencies. The Scanning electron microscope showed that a monolayer of particles was embedded in the image areas. The developed image was placed over a beaker of boiling water for about 15 seconds during which time the pale-blue dye image was imbibed and molecularly dispersed in continuous tone configuration into the hardened gelatin layer. The molecularly dispersed image changed from a pale blue to a brilliant, saturated aesthetically more pleasing cyan hue.

The toner employed in this example was prepared by turnbling one part by weight of cyan with 10 parts by weight polyvinyl alcohol fines with porcelain balls for minutes.

Essentially the same results are obtained by replacing the Staybelite Ester No. 10 light-sensitive element with the Staybelite Ester No. 5 element of example 10, the Staybelite resin F element of example 1 l, the wood rosin light-sensitive element of example 12 and the abietic acid light-sensitive element ofexample 13.

Essentially the same results are obtained by replacing the hardened gelatin'coated paper with polyvinyl alcohol subbed paper and polyvinyl pyrrolidone subbed paper.

EXAMPLE XXVIll Example XXVll was repeated using a toner prepared by forming a l to 3 percent by weight Alphazurine solution in methanol, adding from to 50 grams polyvinyl alcohol (ground to lto lO-microns-diameter along at least one axis) per 100 grams alcoholic solution, agitating for from about 2 to 18 hours, filtering, drying and then tumbling for about l5 minutes to break up the agglomerates. The dye-imbibition image was not quite as brilliant or intense as the imbibed image prepared in example XXVI since less dye was imbibed into the hydrophilic subbing layer. More dye was retained within the polyvinyl alcohol matrix. However, this reproduction was substantially more brilliant and more intense than the image prepared in example XXVll prior to dye imbibition.

EXAMPLE XXIX Example XXVI! was repeated with essentially the same results replacing the Alphazurine 2G dye in the toner with the same weight concentration of Calcocid Phloxine (magenta). The molecularly dispersed dye imbibition image was markedly more brilliant than the embedded image prior to dye imbibition EXAMPLE xxx Example XXVll was repeated with essentially the same results replacing the Alphazurine 2G dye in the toner with the same weight concentration of Tartrazine (yellow). The molecularly dispersed dye imbibition image was markedly more brilliantly than the embedded image prior to dye imbibition.

EXAMPLE XXXl Example XXVll was repeated with essentially the same results replacing the polyvinyl alcohol in the toner with carboxy polymethylene (Carbapol 940 and 941), gelatin and animal glue on an equal basis.

EXAMPLE XXXII This example illustrates the use of a hydrophobic resinous material as a carrier for the hydrophilic dye in dye-imbibition transfer. One and one-quarter grams Staybelite resin, 0.1 gram benzil and 0.3125 gram 4-methyl-7-dimethylaminocoumarin, dissolved in 100 ml. Chlorthene was applied to gelatin-coated paper in the manner described in example XXVll to form a 2.25micron light-sensitive layer. The light-sensitive layer was exposed to light through a continuous-tone positive transparency in the manner described in example XXVll and developed with an Alphazurine 2G-Pliolite VTL toner, described below, in the manner described in example XXVI]. The excellent continuous-tone pale-blue reproduction was imbibed and molecularly dispersed in the gelatin layer by holding the embedded reproduction over boiling water for 15 seconds. The reproduction changed from a pale-blue to a brilliant saturated cyan hue. Photomicrographs of the powder embedded image before and after dye imbibition showed (I) that the light-sensitive layer puddled up when contacted with steam, (2) 90 percent of the embedded particles did not move during steaming, and (3) about 10 percent of the particles, those having the least surface area per volume (largest particles), moved slightly.

The Alphazurine 2G-Pliolite VTL toner was prepared by milling 200 grams of micronized Pliolite VTL and 25 grams Alphazurine 26 on a ball mill with porcelain balls for 64 hours.

Essentially the same results were obtained by replacing the Pliolite VTL in the toner with Piccol'astic DlZS (styrene polymer) and polyisobutyl methacrylate.

A slightly less intense cyan image is obtained by replacing the cyan toner used in this example with a cyan toner prepared by fusing the Alphazurine 2G with Pliolite' VTL inthe manner used to prepare the black' toner of example l. When a cyan toner prepared by fusing 30 parts by weight Alphazurine 2G and parts Pliolite VTL in the manner described in example 1 was used in place of the cyan toner used in this example, a dye-imbibed image of comparable intensity was formed.

EXAMPLE XXXIlI Example XXXII was repeated with essentially the same results using a light-sensitive coating composition consisting of 0.6 gram Staybelite ester No. 10, 0.2 gram Pliolite VTL, 0.21 gram benzil, and 0.15 4-methyl-7-dimethylaminocoumarin.

Essentially the same results are obtained using hot moist air.

EXAMPLE XXXlV This example illustrates the use of Pliolite VTL as the sole film-forming component of a light-sensitive element of this invention. Six-tenths of a gram of Pliolite VTL, 0.21 gram benzil and 0.21 gram 4-methyl-7-dimethylaminocoumarin, dissolved in 100 ml. Chlorothene was flow coated on a gelatin-coated paper substrate in the manner described in example I. The light-sensitive element was exposed to light through a halftone transparency and developed with the toner of example 1 in the manner described therein, forming a halftone image.

EXAMPLE XXXV Example XXXll was repeated with essentially the same results replacing the Pliolite VTL in the toner with 5- to 6- micron rice starch granules and with 12-micron corn starch granules. The principal difference was that the cyan image developed with corn starch was somewhat more saturated than the rice starch image.

EXAMPLE XXXVI This example illustrates dye imbibition of a hydrophobic dye into a hydrophobic subbing layer. Baryta paper bearing a i-mil polyethylene subbing layer was flow coated with a composition consisting of 1.25 grams Staybelite resin, 0.10 gram benzil and 0.316 gram 4-methyl-7-dimethylaminocoumarin, dissolved in 100 ml. Chlorothene. The light-sensitive element was exposed through a metal stencil mask for 60 seconds to a 275-watt sunlamp and developed with rice starch bearing an oil-soluble blue dye in the manner described in example XX- Vll. The element was placed in a chamber of saturated Chlorothene vapors at room temperature for about 20 seconds molecularly imbibing the dye particles into the polyethylene layer.

The developing powder used in this example was prepared by blending 0.2 gram American Cyanamid Oil Blue ZV and 1.80 grams rice starch suspended in Chlorothene, evaporating to dryness on a hotplate at 50 C., and grinding with a mortar and pestle.

Essentially the same results were obtained replacing the blue dye in the developing powder with 0.2 gram American Cyanamid 011 Red N-1700.

Since many embodiments of this invention may be made and since may changes may be made the embodiments described, the foregoing is interpreted as illustrative only and the invention is defined by the claims appended hereafter.

What is claimed is:

l. The process of forming images which consists essentially of:

1. exposing to actinic radiation in image-receiving manner a solid, positive-acting, light-sensitive organic layer having a thickness of from 0.1 to 40 microns, said layer being capable ofdeveloping a R of 0.2 to 22;

. continuing the exposure to clear the background of the light-sensitive layer whereby the most exposed areas are rendered nonpowder receptive;

. applying to said layer of organic material, free-flowing powder particles having a diameter, along at least one axis of at least about 0.3 micron but less than 25 times the thickness of said organic layer;

while the layer is in at most a slightly soft deformable condition and is at a temperature below the melting point of the powder, mechanically embedding said powder partilight-sensitive layer whereby said powder particles displace at least a portion of the light-sensitive layer to yield an image having portions varying in density in proportion to the exposure of each portion; and

5. removing nonembedded particles from said organic layer to develop an image.

2. The process of claim 1, wherein said positive-acting lightsensitive organic layer has a R of 0.4 to 2.0 at room temperature.

3. The process of claim 1, wherein said positive-acting lightsensitive organic layer has a R of at least 0.5, said light-sensitive layer is exposed to actinic radiation in continuous-tone image-receiving manner and developed to form a continuoustone image.

4. The process of claim 1, wherein said positive-acting lightsensitive organic layer is from 0.4- to IO-microns-thick and substantially all of said powder particles are at least 0.5- micron-diameter along one axis.

5. The process of claim 4, wherein said powder particles comprise a polymeric material and at least one member selected from the group consisting of dye and pigment.

6. The process of claim 5, wherein substantially all of said powder particles are at least LO-micron-diameter along one axis and are colored.

7. The process of claim 5, wherein said polymeric material is resinous and said resinous material is fused by heat after said nonembedded particles are removed.

8. The process of claim 5, wherein said polymeric material is resinous, and said resinous material is fused by solvent vapors after said nonembedded particles are removed.

9. The process of claim 6, wherein said developer comprises dyed rice starch.

10. The process for forming images which consists essentially of:

l. exposing to actinic radiation in image-receiving manner a solid, positive-acting, light-sensitive organic layer having a thickness of from 0.1 to 40 microns, comprising a filmforming organic material containing no terminal ethylenic unsaturation, said layer being capable of developing a R of0.4 to 2.0 at room temperature;

. continuing the exposure to clear the background of the light-sensitive layer whereby the most exposed areas are rendered nonpowder receptive;

3. applying to said layer of organic material, free-flowing powder particles having a diameter, along at least one axis of at least about 0.3 micron but less than 25 times the thickness of said organic layer;

. while the layer is at room temperature in at most a slightly soft deformable condition and is at a temperature below the melting point of the powder, mechanically embedding said powder particles as a monolayer in a stratum at the surface of said light-sensitive layer whereby said powder particles displace at least a portion of the light-sensitive layer to yield an image having portions varying in density in proportion to the exposure of each portion; and

5. removing nonembedded particles from said organic layer to develop an image.

11. The process for forming images which consists essentially of:

1. exposing to actinic radiation in image-receiving manner a solid, negative-acting, light-sensitive organic layer having a thickness of from 0.1 to 40 microns, said layer being capable of developing a R of 0.2 to 2.2;

2. continuing the exposure establish a R of 0.2 to 2.2 in the exposed areas whereby powder will adhere to the most exposed areas;

3. applying to said layer of organic material free-flowing powder particles having a diameter along at least one axis of at least about 0.3 micron but less than 25 times the thickness of said organic layer;

4. mechanically embedding said powder particles as a monolayer in a stratum at the surface of said light-sensitive layer whereby said powderparticles displace at least a portion of the light-sensitive layer to yield an image having portions varying in density in proportion to the exposure of each portion while the layer is in at most a slightly soft deformable condition and is at a temperature below the melting point of the powder; and

5. removing nonembedded particles from said to develop an image.

12. The process of claim 11, wherein said negative-acting light-sensitive organic layer is exposed to actinic radiation to establish a R of 0.4 to 2.0 at room temperature 13. The process of claim 11, wherein said negative-acting light-sensitive organic layer is exposed to actinic radiation in continuous tone image-receiving manner to establish a R of at least 0.5 and developed to form a continuous tone image.

14 The process of claim 11, wherein said negative-acting light-sensitive organic layer is from 0.4- to IO-microns-thick and substantially all of said powder particles are at least 0.5- micron-diameter along one axis.

15. The process of claim 14, wherein said powder particles comprise a polymeric material and at least one member selected from the group consisting of dye and pigment.

16. The process of claim 15, wherein substantially all of said powder particles are at least LO-micron-diameter along one axis and are colored.

17. The process of claim 15, wherein said polymeric material is resinous and said resinous material is fused by heat after said nonembedded particles are removed.

18. The process of claim 15, wherein said polymeric material is resinous, and said resinous material is fused by solvent organic layer vapors after said nonembedded particles are removed.

19. The process of claim 1, wherein said light-sensitive layer comprises a solid film-forming organic material and at least one photoactivator selected from the group consisting of primary photoactivators capable of producing free-radicals and superphotoactivators capable of converting light rays into light rays of longer length.

20. The process of claim 11, wherein said negative-acting light-sensitive layer is potentially capable of developing :1 R of at least 0.4 at room temperature and said powder particles are embedded into said light-sensitive layer at room temperature.

21. The process of claim 1 1, wherein said solid, film-forming organic material comprises castor wax.

22. The process of claim 1, wherein said light-sensitive layer comprises a photoactivator in a concentration of 0.1 to 200 percent by weight of the solid, film-forming organic material.

23. The process of claim 22, wherein said light-sensitive layer comprises a superphotoactivator.

24. The process of claim 22, wherein said photoactivator comprises at least one member selected from the group consisting of acyloins and vicinal diketones.

25. The process of claim 24, wherein said photoactivator comprises benzoin in a plasticizing concentration.

26. The process of claim 24, wherein said photoactivator comprises benzil in a plasticizing concentration.

27. The process of claim 1, wherein said light-sensitive layer is on a hydrophilic subbing layer.

28. The process of claim 1, wherein said light-sensitive layer is on a hydrophobic subbing layer.

29. The process of claim 2, wherein said solid film-forming organic material comprises an internally ethylenically unsaturated acid.

30. The process of claim 29, wherein said solid, film-forming organic material comprises a partially hydrogenated rosin acid.

31. The process of claim 2. wherein said solid film-forming organic material comprises an ester of an internally ethylenically unsaturated acid.

32. The process of claim 31, wherein said ester comprises a partially hydrogenated rosin ester.

33. The process of claim 31 wherein said ester comprises a phosphatide.

34. The process of claim 2, wherein said solid film-forming organic material comprises a polymer of an ethylenically unsaturated monomer.

35. The process of claim 34, wherein said polymer comprises a copolymer of vinyltoluene and alpha methyl styrene.

36. The process of claim 2, wherein said solid film-forming organic material comprises a coal tar resin.

37. The process of claim 2, wherein said solid film-forming organic material comprises a halogenated hydrocarbon.

38. The process of claim 37, wherein said halogenated hydrocarbon comprises a halogenated wax.

39. The process of claim 1, wherein said light-sensitive organic layer comprises an aminocoumarin superphotoactivator.

40. The process offorming images which consists essentially of:

l. exposing to actinic radiation in image-receiving manner a solid, light-sensitive organic layer having a thickness of from 0.4 to 10 microns, comprising a film-forming organic material containing no terminal ethylenic unsaturation and a plasticizing concentration of at least one photoactivator selected from the group consisting of primary photoactivators capable of producing freeradicals and superphotoactivators capable of converting light rays into light rays of longer lengths, said layer being capable of developing a R of 0.4 to 2.0 at room temperature;

2. continuing the exposure to clear the background of the light-sensitive layer whereby the most exposed areas are rendered nonpowder receptive;

. applying to said layer of organic material, free-flowing powder particles having a diameter, along at least one axis of at least about 0.3 micron but less than 25 times the thickness of said organic layer;

4. while the layer is at room temperature in at most a slightly soft deformable condition and is at a temperature below the melting point of the powder, mechanically embedding said powder particles as a monolayer in a stratum at the surface of said light-sensitive layer whereby said powder particles displace at least a portion of the light-sensitive layer to yield an image having portions varying in density in proportion to the exposure of each portion; and

5. removing nonembedded particles from said organic layer to develop an image.

41. The process of claim 40, wherein said light-sensitive organic layer comprises at least one solid film-forming organic material selected from the group consisting of an internally ethylenically unsaturated acid, an ester of an internally ethylenically unsaturated acid, a polymer of an ethylenically unsaturated monomer, a coal tar resin, and a halogenated hydrocarbon.

42. The process of claim 40, wherein said solid, film-forming organic material comprises a partially hydrogenated rosin product.

43. The process of forming images which consists essentially of:

l. exposing to actinic radiation in image-receiving manner a solid, light-sensitive organic layer having a thickness of from 0.4 to 10 microns, comprising a film-forming organic material and photoactivator comprising at least one member selected from the group consisting of acyloins and vicinal diketones, said layer being capable of developing a R,,,, of 0.4 to 2.0 at room temperature;

2. continuing the exposure to clear the background of the light-sensitive layer whereby the most exposed areas are rendered nonpowcler receptive;

3. applying to said layer of organic material, free-flowing powder particles having a diameter, along at least one axis of at least about 0.3 micron but less than 25 times the thickness of said organic layer;

4. while the layer is at room temperature in at most a slightly soft deformable condition and is at a temperature below the melting point of the powder, mechanically embedding said powder particlesas a monolayer in a stratum at the ganic material comprises at least one solid, film-forming organic material selected from the group consisting of an internally ethylenically unsaturated acid, an ester of an internally ethylenically unsaturated acid, a polymer of an ethylenically unsaturated monomer, a coal tar resin, and a halogenated hydrocarbon.

47. The process of claim 43, wherein said solid, film-forming organic material comprises a partially hydrogenated rosin product.

v UNITED STATES PATENT OFFICE v CERTEFICATE 0F CGREC'HON Patent NO. 3,637,385 Dated January 25, 1972 Invent0r($) Lester P. Haves; Rexford W. Jones; and William E. Thompson It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 9, line 7, for "large particles." read ---larger particles. Column 11, line 6, for (c) 0G0" read ---(c) O. 10-". Column 13, lines 74 and 75,, ,for "ester of transparency" read ---ester of glycerol) a .7

.- Column 22, line 43, for "effect light-sensitivity" read ---effect on light-sensitivity--- Column 26, line 66, for "exposure establish" read --exposure to establish--.

ll II Column 27, line 10, for R read R Signed and sealed this 27th day of March 1973.

WCSEAUW 7 Attest:

EDWARD M. FLETCHER,JR. ROBERT GOTTSCHALK Attesting Officer Commissioner of Patents FORM PO-1050 (10-69) uscoMM-Dc 60376-P69 US. GOVERNMENT PRINTXNG OFFICE: 1969 0-356-334 

2. continuing the exposure to clear the background of the light-sensitive layer whereby the most exposed areas are rendered nonpowder receptive;
 2. continuing the exposure to establish a Rdn of 0.2 to 2.2 in the exposed areas whereby powder will adhere to the most exposed areas;
 2. continuing the exposure to clear the background of the light-sensitive layer whereby the most exposed areas are rendered nonpowder receptive;
 2. The process of claim 1, wherein said positive-acting light-sensitive organic Layer has a Rdp of 0.4 to 2.0 at room temperature.
 2. continuing the exposure to clear the background of the light-sensitive layer whereby the most exposed areas are rendered nonpowder receptive;
 2. continuing the exposure to clear the background of the light-sensitive layer whereby the most exposed areas are rendered nonpowder receptive;
 3. applying to said layer of organic material, free-flowing powder particles having a diameter, along at least one axis of at least about 0.3 micron but less than 25 times the thickness of said organic layer;
 3. The process of claim 1, wherein said positive-acting light-sensitive organic layer has a Rdp of at least 0.5, said light-sensitive layer is exposed to actinic radiation in continuous-tone image-receiving manner and developed to form a continuous-tone image.
 3. applying to said layer of organic material, free-flowing powder particles having a diameter, along at least one axis of at least about 0.3 micron but less than 25 times the thickness of said organic layer;
 3. applying to said layer of organic material, free-flowing powder particles having a diameter, along at least one axis of at least about 0.3 micron but less than 25 times the thickness of said organic layer;
 3. applying to said layer of organic material free-flowing powder particles having a diameter along at least one axis of at least about 0.3 micron but less than 25 times the thickness of said organic layer;
 3. applying to said layer of organic material, free-flowing powder particles having a diameter, along at least one axis of at least about 0.3 micron but less than 25 times the thickness of said organic layer;
 4. The process of claim 1, wherein said positive-acting light-sensitive organic layer is from 0.4- to 10-microns-thick and substantially all of said powder particles are at least 0.5-micron-diameter along one axis.
 4. while the layer is in at most a slightly soft deformable condition and is at a temperature below the melting point of the powder, mechanically embedding said powder particles as a monolayer in a stratum at the surface of said light-sensitive layer whereby said powder particles displace at least a portion of the light-sensitive layer to yield an image having portions varying in density in proportion to the exposure of each portion; and
 4. while the layer is at room temperature in at most a slightly soft deformable condition and is at a temperature below the melting point of the powder, mechanically embedding said powder particles as a monolayer in a stratum at the surface of said light-sensitive layer whereby said powder particles displace at least a portion of the light-sensitive layer to yield an image having portions varying in density in proportion to the exposure of each portion; and
 4. mechanically embedding said powder particles as a monolayer in a stratum at the surface of said light-sensitive layer whereby said powder particles displace at least a portion of the light-sensitive layer to yield an image having portions varying in density in proportion to the exposure of each portion while the layer is in at most a slightly soft deformable condition and is at a temperature below the melting point of the powder; and
 4. while the layer is at room temperature in at most a slightly soft deformable condition and is at a temperature below the melting point of the powder, mechanically embedding said powder particles as a monolayer in a stratum at the surface of said light-sensitive layer whereby said powder particles displace at least a portion of the light-sensitive layer to yield an image having portions varying in density in proportion to the exposure of each portion; and
 4. while the layer is at room temperature in at most a slightly soft deformable condition and is at a temperature below the melting point of the powder, mechanically embedding said powder particles as a monolayer in a stratum at the surface of said light-sensitive layer whereby said powder particles displace at least a portion of the light-sensitive layer to yield an image having portions varying in density in proportion to the exposure of each portion; and
 5. removing nonembedded particles from said organic layer to develop an image.
 5. removing nonembedded particles from said organic layer to develop an image.
 5. removing nonembedded particles from said organic layer to develop an image.
 5. removing nonembedded particles from said organic layer to develop an image.
 5. The process of claim 4, wherein said powder particles comprise a polymeric material and at least one member selected from the group consisting of dye and pigment.
 5. removing nonembedded particles from said organic layer to develop an image.
 6. The process of claim 5, wherein substantially all of said powder particles are at least 1.0-micron-diameter along one axis and are colored.
 7. The process of claim 5, wherein said polymeric material is resinous and said resinous material is fused by heat after said nonembedded particles are removed.
 8. The process of claim 5, wherein said polymeric material is resinous, and said resinous material is fused by solvent vapors after said nonembedded particles are removed.
 9. The process of claim 6, wherein said developer comprises dyed rice starch.
 10. The process for forming images which consists essentially of:
 11. The process for forming images which consists essentially of:
 12. The process of claim 11, wherein said negaTive-acting light-sensitive organic layer is exposed to actinic radiation to establish a Rdn of 0.4 to 2.0 at room temperature.
 13. The process of claim 11, wherein said negative-acting light-sensitive organic layer is exposed to actinic radiation in continuous tone image-receiving manner to establish a Rdn of at least 0.5 and developed to form a continuous tone image.
 14. The process of claim 11, wherein said negative-acting light-sensitive organic layer is from 0.4- to 10-microns-thick and substantially all of said powder particles are at least 0.5-micron-diameter along one axis.
 15. The process of claim 14, wherein said powder particles comprise a polymeric material and at least one member selected from the group consisting of dye and pigment.
 16. The process of claim 15, wherein substantially all of said powder particles are at least 1.0-micron-diameter along one axis and are colored.
 17. The process of claim 15, wherein said polymeric material is resinous and said resinous material is fused by heat after said nonembedded particles are removed.
 18. The process of claim 15, wherein said polymeric material is resinous, and said resinous material is fused by solvent vapors after said nonembedded particles are removed.
 19. The process of claim 1, wherein said light-sensitive layer comprises a solid film-forming organic material and at least one photoactivator selected from the group consisting of primary photoactivators capable of producing free-radicals and superphotoactivators capable of converting light rays into light rays of longer length.
 20. The process of claim 11, wherein said negative-acting light-sensitive layer is potentially capable of developing a Rdn of at least 0.4 at room temperature and said powder particles are embedded into said light-sensitive layer at room temperature.
 21. The process of claim 11, wherein said solid, film-forming organic material comprises castor wax.
 22. The process of claim 1, wherein said light-sensitive layer comprises a photoactivator in a concentration of 0.1 to 200 percent by weight of the solid, film-forming organic material.
 23. The process of claim 22, wherein said light-sensitive layer comprises a superphotoactivator.
 24. The process of claim 22, wherein said photoactivator comprises at least one member selected from the group consisting of acyloins and vicinal diketones.
 25. The process of claim 24, wherein said photoactivator comprises benzoin in a plasticizing concentration.
 26. The process of claim 24, wherein said photoactivator comprises benzil in a plasticizing concentration.
 27. The process of claim 1, wherein said light-sensitive layer is on a hydrophilic subbing layer.
 28. The process of claim 1, wherein said light-sensitive layer is on a hydrophobic subbing layer.
 29. The process of claim 2, wherein said solid film-forming organic material comprises an internally ethylenically unsaturated acid.
 30. The process of claim 29, wherein said solid, film-forming organic material comprises a partially hydrogenated rosin acid.
 31. The process of claim 2, wherein said solid film-forming organic material comprises an ester of an internally ethylenically unsaturated acid.
 32. The process of claim 31, wherein said ester comprises a partially hydrogenated rosin ester.
 33. The process of claim 31, wherein said ester comprises a phosphatide.
 34. The process of claim 2, wherein said solid film-forming organic material comprises a polymer of an ethylenically unsaturated monomer.
 35. The process of claim 34, wherein said polymer comprises a copolymer of vinyltoluene and alpha methyl styrene.
 36. The process of claim 2, wherein said solid film-forming organic material comprises a coal tar resin.
 37. The process of claim 2, wherein said solid film-forming organic material comprises a halogenated hydrocarbon.
 38. The process of claim 37, wherein said halogenated hydroCarbon comprises a halogenated wax.
 39. The process of claim 1, wherein said light-sensitive organic layer comprises an aminocoumarin superphotoactivator.
 40. The process of forming images which consists essentially of:
 41. The process of claim 40, wherein said light-sensitive organic layer comprises at least one solid film-forming organic material selected from the group consisting of an internally ethylenically unsaturated acid, an ester of an internally ethylenically unsaturated acid, a polymer of an ethylenically unsaturated monomer, a coal tar resin, and a halogenated hydrocarbon.
 42. The process of claim 40, wherein said solid, film-forming organic material comprises a partially hydrogenated rosin product.
 43. The process of forming images which consists essentially of:
 44. The process of claim 43, wherein said photoactivator comprises benzoin in a plasticizing concentration.
 45. The process of claim 43, wherein said photoactivator comprises benzil in a plasticizing concentration.
 46. The process of claim 43, wherein said film-forming organic material comprisEs at least one solid, film-forming organic material selected from the group consisting of an internally ethylenically unsaturated acid, an ester of an internally ethylenically unsaturated acid, a polymer of an ethylenically unsaturated monomer, a coal tar resin, and a halogenated hydrocarbon.
 47. The process of claim 43, wherein said solid, film-forming organic material comprises a partially hydrogenated rosin product. 